Many communications and RADAR systems operate at RF frequencies of Ku Band or higher. In many of these systems it is necessary to continuously monitor and adjust the transmitted RF power level and the gain of the receiver (or transmitter) in order to compensate for changing link conditions such as atmospheric changes in weather conditions, interference, movement or changes in orientation of the terminals. To accomplish this, RF power levels are sampled using an RF power detector and RF gain or signal levels are adjusted as appropriate. Since many transmission systems are pulsed in nature, the RF power detector for a pulsed transmission system must be able to react and settle to a stable measurement value fast enough to accurately measure the RF pulse before the pulse ends.
At these frequencies, commercially available RF power sensors have limited sensitivity, pulse settling speed, dynamic range and accuracy. They also tend to be large in size making them inadequate for many potential applications. A few commercially available RF power sensors have relatively small dimensions of less than 0.3″×2.5″×3″. These power detectors, however, have limited operating frequencies or environmental sensitivities that limit their use to applications with operating frequencies of 25 GHz or less or applications that have laboratory like environmental conditions.
RF power sensors operating in these regions have limited sensitivity, pulse settling speed, dynamic range and accuracy for a variety of reasons. The RF signals are frequently low in power have fairly low signal to noise temperature ratios. Inductive noise currents and component variations often add unwanted noise and errors. Temperature and environmental changes frequently effect component response and add Direct Current (DC) and low frequency biases into the amplification circuits. Other low frequency and DC noise sources sometimes introduce significant errors in power measurement.
Those skilled in the art will recognize that there is a need for a small sensitive and accurate RF power detector having a wide dynamic range for sensing short pulses of very high frequency signals in a variety of environments. The invention addresses this need as well as others.